The thrust of this project is to uncover specific functional alterations in the brain-pituitary-testis axis of aged male mice. Questions concerning age related alterations in the neural components regulating reproduction are being investigated by evaluating functional alterations in sensory pathways affecting LH release and sexual behavior. Pituitary function is being evaluated from the standpoint of LH, FSH, and PRL secretion and by evaluating the number of cells in the pituitary gland containing these peptide hormones. Testis function is being evaluated by measuring steroids in the testicular venous effluent of in vitro perfused testes.